The mayor grew up in a building so decrepit — filthy hallways, no private toilets, no showers — that his friends in nearby concrete towers pitied him.

Five decades later, that building — in St.-Ouen, a Paris suburb — is a distant memory, and in its place rises France’s Olympic pride: the athletes’ village, with its architectural-showcase buildings that are outfitted with solar panels, deep-sinking pipes for cooling and heating, and graceful balconies from which to look down on the forest planted below. One-quarter will become public housing after the Games.

“All of a sudden, we have the same feeling of pride as people living in the hypercenter,” said the mayor of St.-Ouen, Karim Bouamrane, 51, using his personal shorthand for the glamorous downtown playgrounds of the elites. “There was Los Angeles, Barcelona, Beijing, London, Sydney and, now, there is St.-Ouen.”

Even before the Olympic Committee choose to invest in this economically depressed northern suburb, St.-Ouen was changing. But since then, and since Mr. Bouamrane’s election as mayor in 2020, the transformation seems turbocharged.

Dump trucks rumble throughout the small city, including in front of the 160-year-old City Hall, where jackhammers and excavators claw at the pavement, following plans to green the adjacent plaza with trees and benches.

At the center of the activity is Mr. Bouamrane, a member of the Socialist Party, who is in the news a lot these days as St.-Ouen prepares to welcome the Olympic athletes.